The Shadow Matrix by Marion Zimmer Bradley is the sequel to Exile Star. Margaret Alton and Mikhail Lanart-Hastur are both facing new challenges and responsibilities as they are further drawn into the Comyn heirarchy. Mikhail must combat the sinister leronis who holds Priscilla Elhalyn and her family in thrall, while Margaret must learn to control the mysterious shadow matrix imprinted upon her hand.

Then, they are suddenly called backwards in time by Varzil the Good, who is dying and wants to pass his matrix ring on to someone he can trust to use it properly. He also insists that they must be married di catenas to properly link their laran. After he dies, they are rescued by a company of Sword Sisters, who take them to an old castle where Mikhail can recover from matrix shock. They are then captured by Padraic El Haliene, who is trying to build nuclear weapons. They foil him and then return to their own time and settle up the succession.

Overall, I found this a very weak book. It is diffuse and wastes far too many of its pages on senseless exposition and talking heads. I'd suggest saving your money to buy new copies of some of the older Darkover books.